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  1.   1.  Where one can set a config
  2.   2.  ASUS 550
    1.   2.1  Best result on Nov 24, 2017
    2.   2.2  First try (for archives)
  3.   3.  manual

similar solution:

https://forums.opensuse.org/showthread.php/507397-Adjusting-screen-resolution-on-a-system-with-no-monitor-connected

1.  Where one can set a config

Beware, it's easy to forget that you setup some file, there are a number!

 /etc/X11/xorg.conf.d/

Where 50-monitor.conf and 50-screen.conf are the place of choice for X. See man xorg.conf for syntax.

 Option "TransformationMatrix" "a b c d e f g h i"

seen on the web is only for input devices, not screen.

 /etc/X11/xinit/

and

 /etc/X11/xinit/xinitrc.d

(any file) - seen in logs at the very end of the file - but there the "panning" option of xrandr is not ack.

If you want to change all the system. The same file in ~/.xinitrc for user setup (a template file is available in openSUSE as example, with place for user change).

 /etc/bumblebee/xorg.conf.nouveau

Virtual x y have to be in Screen/Display

In ~/.config/Autostart one can set a bash file, made executable, activated in kde setup/"start and stop"

also ~/.xinitrc and ~/.bashrc

May also be in ~/.config/monitor.xml

etc/init.d/after.local

2.  ASUS 550

2.1  Best result on Nov 24, 2017

First lines are for reference, three last real action, to be inserted in kde/start and stop/add script

Inserted in a text file

#xrandr --newmode "hd"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync
#xrandr --addmode VIRTUAL1 hd
#xrandr --output VIRTUAL1 --panning 1920x1080
#xrandr --output eDP1 --scale-from 1920x1080 --panning 1920x108
#xrandr --dpi 96 --output eDP1 --mode 1366x768 --scale-from 1920x1080 --panning 1920x1080

xrandr --newmode "1920x1080"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync
xrandr  --addmode VIRTUAL1 1920x1080
xrandr --fb 1920x1080 --dpi 96 --output eDP1 --pos 0x0 --scale-from 1920x1080 --same-as VIRTUAL1

the first lines, as comments, are just for reference

There are three useful lines. The first is the standard mode creation as 1920x1080. Using "hd" for name didn't show in the kde setup GUI. Second line creates the virtual screen. Third line create the frame buffer for virtual and place it in a good position.

2.2  First try (for archives)

My Version of this computer have an "AUO Model 47ec 2013, B156XW004.7, 18412" screen. Looks like the "XW" means the screen is only 1366x768 (https://fr.wikipedia.org/wiki/Wide_Extended_Graphics_Array).

Then, I try to scale the screen to have a similar result

nothing works really. The best I can do is boot with scale, but I have to run panning after boot, so Kde do not really see it, then the black part on the screen where only applications can be set, no background nor plasmoid.

3.  manual

On DEll 755 (vga Intel, TV), manually:

$ cvt 1920 1080 60
$ 1920x1080 59.96 Hz (CVT 2.07M9) hsync: 67.16 kHz; pclk: 173.00 MHz
Modeline "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync

$xrandr --newmode "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync

$xrandr --addmode VGA1 "1920x1080_60.00"

xrandr --output VGA1 --mode 1920x1080_60.00

To make it permanent, one need to edit files in /etc/X11/xorg.conf.d/50-*

Section "Monitor"
 Identifier "TV"

 VendorName "BELSON"
 HorizSync 31.0 - 84.0
 VertRefresh 56.0 - 77.0

Modeline "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync

Option "PreferredMode" "1920x1080_60.00"
EndSection

Section "Screen"

  Identifier "VGA1"
  Device "VGA1"
  Monitor "TV"
  DefaultDepth 24
  SubSection "Display"
    Depth 24
    Modes "1920x1080_60.00"
  EndSubSection

EndSection 

take attention to the fact that xorg stores somewhere the used resolution and start with it, so you may need to issue "xrandr" to verify is the new resolution is recorded, then "xrandr --output VGA1 --mode 1920x1080_60.00" to use it the first time.